Without -O flags you get debug-level and all function inlining is disabled, depending on the code it can make a huge difference indeed. But Pd is probably compiled with at least -O2. So the flags don't make much difference. The compiler? Doesn't Miller compile with MinGW nowadays, I don't know. MinGW brings its own standard C libs, which may implement math functions differently than MS. But regarding denormals I guess they both respect the IEEE 754 standard.
You can check if you really have subnormals using attached patch denorm-test.pd you. The patch tests lop~, change it to bob~. On Wed, Sep 21, 2016 at 11:18 PM, Christof Ressi <[email protected]> wrote: > the SSE optimizations don't seem to matter at all. skipping -ffast-math gives > a slight overall CPU rise, while skipping -O3 gives me huge CPU rise (20 bob~ > filters are already to much for one core). Even when skipping all of those > flags, the denormals issue is still not present. > > Maybe it has something to do with the compiler? > >> Gesendet: Mittwoch, 21. September 2016 um 22:47 Uhr >> Von: katja <[email protected]> >> An: "Christof Ressi" <[email protected]>, "[email protected]" >> <[email protected]> >> Betreff: Re: Re: [PD] [bob~] denormals issue? >> >> I'm curious to know if the flags do flush denormals on your processor. >> Forgot to mention that '-O3 -ffast-math' are also set, >> platform-independent. So if you have a chance to try which flag does >> something... It's just curiosity. >> >> On Wed, Sep 21, 2016 at 10:34 PM, Christof Ressi <[email protected]> >> wrote: >> > Hi Katja, >> > >> >> Even if your test reveals a beneficial effect from compiler flags, >> >> it is better when denormals are detected and flushed in the C code. >> > >> > definitely! Maybe using the PD_BIGORSMALL macro on each filter state at >> > the end of the DSP routine does the trick, just like in all the other >> > recursive filters in Pd. >> > >> > >> > >> >> Von: katja <[email protected]> >> >> An: "Christof Ressi" <[email protected]> >> >> Cc: pd-list <[email protected]>, "Miller Puckette" <[email protected]> >> >> Betreff: Re: [PD] [bob~] denormals issue? >> >> >> >> Hi Christof, >> >> >> >> Makefile.pdlibbuilder passes flags '-march=pentium4 -msse -msse2 >> >> -mfpmath=sse' for optimization to the compiler on Windows. You could >> >> try compiling without (some of) these flags to see if they are >> >> responsible for the different behavior. Makefile-defined optimization >> >> flags can be overriden with argument CFLAGS given on command line. >> >> >> >> The effect of optimization flags on denormals varies per processor >> >> type, unfortunately. When we had denormals on Raspberry Pi ARMv6 they >> >> wouldn't go away no matter what flags, is what I remember. Even if >> >> your test reveals a beneficial effect from compiler flags, it is >> >> better when denormals are detected and flushed in the C code. Anyway, >> >> it is still interesting to know what makes the difference. >> >> >> >> Katja >> >> >> >> On Wed, Sep 21, 2016 at 12:32 AM, Christof Ressi <[email protected]> >> >> wrote: >> >> > Hmmm... I compiled [bob~] myself with MinGW and pd-lib-builder and I >> >> > noticed two things: >> >> > 1) the CPU rise is gone >> >> > 2) it needs only half the CPU. I put 20 [bob~] objects in a switched >> >> > subpatch and measured the CPU load. The DLL which comes with the >> >> > Windows binaries needs 15%, while my own DLL needs only 7%! That's >> >> > quite a deal... >> >> > >> >> > Christof >> >> > >> >> > PS: I attached the DLL in case you wanna try it yourself. >> >> > >> >> > >> >> >> Gesendet: Samstag, 17. September 2016 um 22:58 Uhr >> >> >> Von: "Christof Ressi" <[email protected]> >> >> >> An: [email protected], "Miller Puckette" <[email protected]> >> >> >> Betreff: [PD] [bob~] denormals issue? >> >> >> >> >> >> Hi Miller, >> >> >> >> >> >> feeding audio into [bob~] and then going to zero will increase the CPU >> >> >> load by ca. 6%. Clearing the filter or adding a tiny amount of noise >> >> >> brings the CPU load back to its usual level immediately, so I guess >> >> >> it's a problem with denormals. >> >> >> My Pd load meter won't really show the increase, but it's clearly >> >> >> visibly on Process Explorer. >> >> >> >> >> >> See my attached patch. Tried with Pd 0.47.1, Lenovo Thinkpad L440, >> >> >> Windows 7. >> >> >> >> >> >> Christof_______________________________________________ >> >> >> [email protected] mailing list >> >> >> UNSUBSCRIBE and account-management -> >> >> >> https://lists.puredata.info/listinfo/pd-list >> >> >> >> >> > _______________________________________________ >> >> > [email protected] mailing list >> >> > UNSUBSCRIBE and account-management -> >> >> > https://lists.puredata.info/listinfo/pd-list >> >> > >> >> >>
#N canvas 129 301 620 382 10; #X symbolatom 18 351 72 0 0 0 - - -; #X obj 18 323 makefilename %.70f; #N canvas 0 50 190 245 nan 0; #X obj 45 17 inlet; #X obj 46 173 outlet; #X obj 45 74 t b f; #X msg 46 96 2; #X obj 46 143 * 0; #X obj 46 118 pow 1024; #X msg 45 49 1024; #X connect 0 0 6 0; #X connect 2 0 3 0; #X connect 2 1 5 1; #X connect 3 0 5 0; #X connect 4 0 1 0; #X connect 5 0 4 0; #X connect 6 0 2 0; #X restore 18 44 pd nan; #X obj 18 20 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1 -1; #N canvas 0 50 168 259 inf 0; #X obj 45 17 inlet; #X obj 46 173 outlet; #X obj 45 74 t b f; #X msg 46 96 2; #X obj 46 118 pow 1024; #X msg 45 49 1024; #X connect 0 0 5 0; #X connect 2 0 3 0; #X connect 2 1 4 1; #X connect 3 0 4 0; #X connect 4 0 1 0; #X connect 5 0 2 0; #X restore 71 44 pd inf; #X obj 71 20 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1 -1; #X floatatom 18 181 8 0 0 0 - - -; #X msg 72 116 1; #X msg 72 86 0; #X msg 106 202 \; pd dsp 1; #X msg 106 241 \; pd dsp 0; #X obj 106 179 loadbang; #N canvas 0 50 200 224 unsig~ 0; #X obj 32 40 inlet~; #X obj 32 122 snapshot~; #X obj 61 89 metro 200; #X obj 61 62 tgl 15 1 empty empty empty 17 7 0 10 -262144 -1 -1 1 1 ; #X obj 32 153 outlet; #X connect 0 0 1 0; #X connect 1 0 4 0; #X connect 2 0 1 0; #X connect 3 0 2 0; #X restore 18 266 pd unsig~; #X floatatom 18 296 17 0 0 0 - - -; #X text 183 133 Small floats which can't be expressed with the bits of the datatype are also denormal \, more specifically: subnormal. Computations with subnormal numbers are still possible \, but very CPU intensive. Test: click 1 first \, then 0 to see how small the numbers become. If all is OK \, numbers smaller than ~1e-19 are flushed to zero. If not OK \, numbers smaller than 1e-39 are seen. These are subnormals. Check CPU load difference. It is always possible to recover from subnormals by sending a normal number (like 1) in.; #X text 184 320 Katja Vetter Jan 2013; #X obj 18 216 lop~ 1; #X text 183 261 IIR filters have internal feedback delay lines \, therefore objects like [lop~] \, [hip~] and [biquad~] must be protected against denormals.; #X text 183 18 NaN and inf are denormal numbers. When inf or nan starts recirculating in a feedback delay line \, the object can't do further calculations \, even if the input goes back to normal. Therefore Pd must avoid writing nan or inf into a feedback delay line. Test: click nan or inf first \, and 1 thereafter. If all is OK \, the output returns to normal. If not OK \, inf or nan will stay at the output and the patch must be reloaded to recover.; #X connect 1 0 0 0; #X connect 2 0 6 0; #X connect 3 0 2 0; #X connect 4 0 6 0; #X connect 5 0 4 0; #X connect 6 0 16 0; #X connect 7 0 6 0; #X connect 8 0 6 0; #X connect 11 0 9 0; #X connect 12 0 13 0; #X connect 13 0 1 0; #X connect 16 0 12 0;
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